1. Field of the Invention
The present invention relates to a single use syringe. More specifically, this invention relates to an arrangement designed to separate the plunger from the plunger rod after a single use to thereby prevent needle sharing among drug addicts or patients, which has been a major contributor to the transmittal of viral infections such as AIDS.
This invention also includes a cap to be placed over a needle subsequent to syringe use to prevent a noninfected person from being pricked with the needle after its use. Such accidents usually occur when a nurse, doctor, lab technician, relative or friend draws a blood sample or administers an injection to a known or unknown HIV infected person.
The syringe of the present invention also includes a tube-type backstop which prevents removal of the plunger rod from the barrel of the syringe, thereby precluding the interchange of parts between syringes.
2. Description of the Prior Art
Single use syringes are known in the prior art. U.S. Pat. No. 4,820,272 issued Apr. 11, 1989 to Michele M. Palmer discloses a non-reusable hypodermic syringe which uses downwardly slanted teeth disposed internally of the syringe barrel to limit movement of the plunger and the piston connected thereto to a single direction, the teeth preventing retraction of the plunger in the opposite direction.
U.S. Pat. No. 4,878,899 issued Nov. 7, 1989 to Frederick L. Plouff discloses a disposable syringe for one time use comprising a plurality of resilient pins disposed longitudinally of a syringe barrel and internally thereof, and biased to engage the plunger or piston once the plunger or piston has passed the ends of the resilient pins, the pins serving to prevent the retraction of the plunger.
U.S. Pat. No. 5,084,018 issued Jan. 28, 1992 to Chien-Hua Tsao discloses a safety syringe wherein the end of the plunger and the needle collapse into the hollow plunger rod after the plunger rod has been displaced to the end of the barrel.
U.S. Pat. No. 5,114,405 issued May 19, 1992 to Douglas A. Winter discloses a single use, tamper resistant syringe having a plunger slidable within a cylinder retained within a barrel, the cylinder including a pair of biased dogs which are engageable with a surface of the plunger when fully depressed to prevent retraction of the plunger, the dogs engaging a top surface of a cap or piston mounted on the plunger to separate the plunger and the cap or piston when not fully depressed to prevent removal of the plunger and the cap or piston when not fully depressed.
French Patent No. 2,646,086 issued Oct. 26, 1990 to Francis Pons discloses a plastic syringe which is separable from a plunger after a single use by disengaging convergent fingers integral with a piston by a camming means on the plunger.
French Patent No. 2,653,340 issued Apr. 26, 1991 to Monie Jean discloses a single use syringe having a separable ring and conical coupling whereby a piston is separated from a plunger after the plunger has been fully depressed.
U.S. Pat. No. 5,066,279 issued Nov. 19, 1991 discloses a protective sheath for encasing a hypodermic needle before and after use.
None of the foregoing patents, taken either alone or in combination, disclose or suggest the instant invention as described and claimed below.